LONDON — Not even an overseas trip or a potentially overlooked opponent could stop the 49ers’ win streak from reaching five in dominant fashion Sunday.

The 49ers won 42-10 at storied Wembley Stadium after insisting all week they wouldn’t take lightly their winless foe, the Jacksonville Jaguars.

“We have the most paranoid coaching staff in the National Football League,” safety Donte Whitner said. “We go over things so many times that by the time you get to the game, it’s embedded in your brain. They made sure we didn’t come out here sleepwalking.”

Coach Jim Harbaugh and his staff creatively crafted a game plan that delivered four touchdowns on the 49ers’ first four possessions for a 28-0 lead.

“Our preparation was outstanding,” Harbaugh said. “Players were dialed in. They did a great job in practice and off the field, in their free time. Curfews were 100 percent each night.”

After one more night in London, the 49ers (6-2) will fly home Monday and head into a bye week, with only “opportunity practices” scheduled Tuesday and Wednesday for players who wish to attend, such as those coming off injured lists.

The 49ers put on the second-highest scoring show since the NFL began exporting regular-season games here in 2007, topped only by the New England Patriots’ 45-7 win last year over the St. Louis Rams. The 49ers’ season-high point total also marked their fifth straight game over 30 points.

To illustrate how things went according to script, look no further than offensive coordinator Greg Roman’s second play call, titled: “Big Sleeper.” Fullback Bruce Miller headed to the 49ers sideline, stopped short of it and “hid” there uncovered so Kaepernick could toss him a quick pass that Miller rumbled with for a 43-yard completion.

“Shhh, we’ll run it again. Don’t let them know about the ‘Sleeper,’ ” Miller said. “It was a great play call. Timing was great. The only way it could have gone any better was if I was any faster.”

Miller feared he might jump offside or drop the ball before the Jaguars (0-8) could rush to cover him. Kaepernick kept calm and carried on with his job, stating, “You try to give him an easy pass he can catch in the chest and keep running down the sideline.”

That tone-setting drive later saw Gore convert on a fourth-and-1 run, then, two snaps later, dart 19 yards up the middle for his first touchdown and a 7-0 lead.

Two touchdown runs by Kaepernick were sandwiched around his 2-yard touchdown pass to tight end Vernon Davis. A 2-yard, third-quarter plunge marked Gore’s second touchdown of the game and the first time in his career he’s produced two rushing touchdowns in back-to-back games.

“The offense came out very strong and put together great scoring drives with great execution,” Harbaugh said.

The 49ers defense wasn’t rubbish, either.

Dan Skuta’s 47-yard fumble return gave the 49ers a sixth touchdown. Fellow linebacker Patrick Willis’ second forced fumble in three games (see: strip of Arizona’s Larry Fitzgerald) set up Skuta’s score.

“It was an easy play for me. I just had to get to the end zone,” Skuta said. “That’s the first real running I’ve done with the ball in quite awhile.”

The sight of a 250-pound linebacker lumbering across the goal line produced one of the loudest roars of the night from the 83,559 watching the NFL’s second game in a month at Wembley. (The Minnesota Vikings defeated the Pittsburgh Steelers 34-27 here Sept. 29.)

“It got pretty loud. It was cool,” Skuta said.

The atmosphere also won over Harbaugh, who said he felt as though he were at an Olympic medal ceremony when America’s national anthem was followed by “God Save the Queen.”

“It was an amazing experience for our players and me personally,” Harbaugh said. ” … I really got a chill when that gal was singing, ‘God Save the Queen.’ Great experience.”

Those emotions might have been the only thing that caught Harbaugh off guard all night. Echoing his earlier statement, Whitner made sure to single out Harbaugh as the NFL’s most paranoid coach.

“It doesn’t matter who we’re playing, if it’s the last play of a football game, if it’s the last play of a practice,” Whitner said. “He makes sure we’re on our P’s and Q’s. That’s why we have such a good coaching staff. They understand players can tend to take their foot off the gas, and they won’t allow us to.”

Left tackle Joe Staley agreed: “It’s great to be paranoid. It’s great to never play comfortable, always thinking about worst-case scenario beforehand.”

After five straight wins, there haven’t been many worst-case scenarios lately.

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